Freestanding GaN substrate enabled by dual-stack multilayer graphene via hydride vapor phase epitaxy

•The growth of freestanding GaN on dual-stack multilayer graphene has been presented.•The FWHM of rocking curves of GaN for (0 0 2) and (1 0 2) are 301 and 525 arcsec.•The Raman spectra prove the separation occurs between dual-stack graphene layers.•This study provides a feasible way to obtain high-quality and large size GaN substrate.